1. Technical Field
The present invention relates to an image recording apparatus for creating a holographic stereogram recorded so that a photographed image or a computer-generated image can be observed three-dimensionally.
2. Description of Related Art
To create a holographic stereogram, for example, a subject is photographed from different observation points to generate many images as original pictures. These images are sequentially recorded as strip or dot element holograms on a single holographic recording medium.
For example, FIG. 1 shows a holographic stereogram having parallax information in a cross direction only. A subject 90 is sequentially photographed crosswise from different observation points to generate a plurality of original pictures 91a to 91e. An image recording apparatus sequentially records these original pictures as element holograms in strips on a holographic recording medium 92.
Image information is obtained by sequentially photographing from different observation points along a cross direction and is sequentially recorded crosswise as element holograms in strips. When an observer views this holographic stereogram with both eyes, right and left eyes accept slightly different 2-D images respectively. This causes the observer to feel parallax, reproducing a 3-D image.
FIG. 2 shows a configuration example of a printer for creating such a holographic stereogram (hereafter referred to as a holographic stereogram printer). FIG. 2(A) is atop view of an entire optical system for a holographic stereogram printer 100. FIG. 2(B) is a side view of an object light portion of the optical system.
The holographic stereogram printer 100 captures many image data elements by crosswise photographing a real object from different observation points. Processed image data includes rendering images such as a plurality of CAD (Computer Aided Design) or CG (Computer Graphics) images created by sequentially providing parallaxes crosswise. Based on the processed image data, the holographic stereogram printer 100 drives an LCD (Liquid Crystal Display). 109. Each image data is sequentially recorded as a hologram strip on a holographic recording medium 112 for creating a holographic stereogram.
Actually, in this holographic stereogram printer 100, a separately provided system control section drives an LCD 108 based on one of a plurality of generated image data. The LCD 108 displays an image based on the image data. At this time, the system control section sends a control signal to a shutter 114 to open it. A laser beam L10 generated from a laser light source 101 enters a spatial filter 104 via the shutter 114, a half mirror 102, and a mirror 103, sequentially.
This laser beam L11 is enlarged by the spatial filter 104 and a collimator lens 105. The beam is transmitted through the LCD 108 and is converted to projection light corresponding to an image displayed on the LCD 108. The beam then enters a cylindrical lens 107 via a condensing lens 106. The beam is crosswise condensed by the cylindrical lens 107 and then enters a holographic recording medium 112 mounted on an electric stage 113.
When the laser beam is applied to the holographic recording medium 112, the laser beam L12 reflected on the half mirror 102 is transmitted through the cylindrical lens 109, the collimator lens 110, and a mirror 111 in order. As reference light, the laser beam enters at a specified angle from the rear side of the holographic recording medium 112. In this case, the optical path length of the reference light is specified so that it becomes approximately the same as the optical path length of a laser beam (hereafter referred to as an object light) which passes the half mirror 102 and then the mirror 103 and enters the holographic recording medium 112.
The holographic stereogram printer 100 can let the object light (projection light) and the reference light interfere with each other on a recording surface of the holographic recording medium 112. Consequently, an image displayed on the LCD 108 can be recorded as an interference pattern in strips on the holographic recording medium 112.
When the image has been recorded in this holographic stereogram printer 100 thereafter, the system control section drives the shutter 114 to block the laser beam L10 generated from the laser light source 101. The LCD 108 is also stopped. Under control of the system control section, the electric stage 113 is driven to feed the holographic recording medium 112 for the width of one hologram strip in the direction of an arrow b.
Under control of the system control section thereafter, the LCD 108 is driven to display an image based on the succeeding image data: Then, the system control section opens the shutter 114 to record the image displayed on the LCD 108 onto the holographic recording medium 112. After that, the operation is repeated successively.
Hence, the holographic stereogram printer 100 can successively record images in strips onto the holographic recording medium 112 based on image data in a supplied parallax image sequence. This can provide a desired holographic stereogram.
The above-mentioned holographic stereogram printer needs a means for holding and transferring a holographic recording medium. Such means must completely fix the holographic recording medium during exposure, cause no vibration as small as a wavelength, fast transfer the medium and leave no vibration after a stop. However, it takes approximately 2 seconds for the electric stage 113 of the holographic stereogram printer 100 until a vibration attenuates after the transfer. When this electric stage 103 is used to transfer the medium each time a hologram strip is formed, it will take a very long time until one holographic stereogram is completed.
An examination was conducted concerning the holding and transfer means capable of suppressing the vibration of the holographic recording medium. Instead of the above-mentioned electric stage 113, a method has been devised to load a long holographic recording medium between two parallel rollers, use a torsion coil spring or the like to provide a given tension for support, and irradiate object light by pressing optical parts against a bridge between the two parallel rollers. This configuration can decrease the time for attenuating the vibration after the transfer to a quarter or less. However, there is a problem of complicating the mechanism for allowing the torsion coil spring to stably generate a given force.
As with a conventional printer or printing apparatus, it is possible to generate easily a given torque without using a torsion coil spring by always rotating a slip material reversely and transmitting a motor drive to one of the parallel rollers. Since the motor rotates even during exposure of the hologram, this rotation generates an unnecessary vibration, deteriorating the image quality.
Applying an excess tension to such a film material in the longer direction easily ripples the film surface and prevents the film from being parallelized. This caused an image to be distorted or to lose uniformity.
When a holding method is used to cause a large stress difference between the longer and shorter directions, double refraction occurs on a base filth or a cover film. This also could cause image deterioration. When the medium is pressed against a glass, a dust particle enters to lift the exposed portion. This also ripples the film and gives a disadvantageous effect on the image.
It is an object of the present invention to provide an image recording apparatus which can simply and reliably prevent a holographic recording medium from vibrating. It also is an object of the present invention to provide a holographic recording medium cartridge which can protect the holographic recording medium against external dust and the like.
For solving the above problems, an image recording apparatus according to the present invention irradiates object light to one side of a holographic recording medium and reference light to the other side thereof and successively records each image in a parallax image sequence as an element hologram on the holographic recording medium, comprising: transfer means for transferring the holographic recording medium; and medium retaining means for retaining an exposure portion vicinity of the holographic recording medium transferred by the transfer means by using two members each having a cutout for transmitting the object light or the reference light.
In this image recording apparatus, the medium retaining means holds the holographic recording medium in the thickness direction near the exposure portion. For doing so, the medium retaining means uses a contact member touching the holographic recording medium and a presser plate member letting the holographic recording medium closely contact with this contact member. Accordingly, it is possible to suppress vibration generated on the holographic recording medium during exposure.
For solving the above problems, a holographic recording medium cartridge attached to an image recording apparatus uses a holographic recording medium to record sequentially, as an element hologram, an interference pattern generated from an object light processed by image modulation based on each image in a parallax image sequence and a reference light having coherence to this object light. The cartridge integrates a shading container winding the continuous holographic recording medium round a rotatively contained shaft and shading external light; and medium retaining means for retaining an exposure portion vicinity of the holographic recording medium pulled out of a feeding opening in the shading container by using two members each having a cutout for transmitting the object light or the reference light.
This holographic recording medium cartridge can prevent the holographic recording medium from being exposed outward up to the medium retaining means and protect it against external dust and the like.
As will be clearly understood from the above description, the image recording apparatus according to the present invention can sufficiently suppress vibration during a recording operation on a holographic recording medium. This enables accurate recording and improves diffraction efficiency during reproduction, generating a bright and clear holographic stereogram. The film flatness is maintained well, preventing an image from being distorted.
It is possible to greatly reduce wait time until the vibration attenuates after the holographic recording medium is transferred. Accordingly, it is possible to greatly shorten process tune when the holographic recording medium is transferred for creating a holographic stereogram each time one hologram strip is recorded.
The holographic recording medium cartridge according to the present invention improves maintainability and prevents lifting and image quality degradation due to a dust particle entered between the holographic recording medium and a contact member.